The present invention relates to the preparation of antigens of and of vaccines for the virus of Mystery Disease, as well as to the antigens and to the vaccines obtained.
The disease called Mystery Disease (M.D.) or also Porcine Reproductive Respiratory Syndrome (P.R.R.S.) began to acquire an identity of its own in pigs, in 1986 in the United States and in 1990 in Europe. This disease manifests itself essentially in pigs by signs of exhaustion, anorexia and hyperthermia of the order of 40.degree. C., which are conventionally observed in sows in pig farms affected by the disease. These signs are accompanied or followed by reproductive disorders (premature or late farrowing and birth of stillborn, mummified or sickly piglets, and return of the sows to heat). A respiratory syndrome can be observed in piglets with interstitial pneumonia lesions. Older pigs can also be affected by respiratory disorders. All this symptomatology can be accompanied by diseases caused by chance infections conventionally observed in pigs.
In G. Wensvoort et al., Mystery Swine Disease in the Netherlands: the isolation of Lelystad virus, The Veterinary Quarterly, Vol. 13, No. 3, 19 Jul. 1991, the isolation of an agent associated with the disease called Mystery Disease is described, which is characterized as a virus, designated Lelystad virus, and which is presented as the causative agent of the disease. This discovery might constitute a first step for the search for a vaccine against this disease.
A process for the industrial production of this virus or of antigen of this virus was not available, the culture seeming possible only in pig alveolar macrophages.